In this type of floor conveyor, in order to narrow the width of the slit, it is necessary to narrow the width of a transverse sectional shape of the columnar support member supporting the conveyed object support base portion on the upper side of the floor surface. On the other hand, in order to obtain necessary load-bearing performance, the length in a traveling direction is lengthened. Since in general, two front and rear portions of the conveyed object are supported by the columnar support members, the two front and rear columnar support members are configured so as to maintain a fixed posture relative to each other. Consequently, when the conveying traveling body on the lower side of the floor surface travels along a horizontal curved path section, the two front and rear columnar support members move within the slit in the horizontal curved path section so as to have an oblique posture in plain view, and thus it is necessary to widen the width of the slit in the horizontal curved path section. If the width of the slit is wide, when the conveying traveling body does not travel, there is a danger that a foreign object or a foot of an operator walking on the floor surface is caught therein. In order to avoid such a danger, for example, as disclosed in Japanese Published Unexamined Patent Application No. H07-277178 (Patent Literature 1), it is considered that an auxiliary floor surface member which is normally in such a horizontal posture so as to narrow the width of the slit but which is pushed upward by the columnar support member when the columnar support member passes therethrough is additionally provided on a side of the slit in the horizontal curved path section.